diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index aa60e78..57df427 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,7 +17,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
-        pip install --upgrade -r requirements.txt -r requirements-dev.txt
+        pip install --upgrade -r requirements-dev.txt
         pip install .
     - name: Run tests
       run: |
diff --git a/MANIFEST.in b/MANIFEST.in
index e58eddb..78c6184 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,5 +1,6 @@
 include *.py
 include *.toml
+include requirements-dev.in
 include *.txt
 include CHANGES
 include COPYING
diff --git a/requirements-dev.in b/requirements-dev.in
new file mode 100644
index 0000000..dbe389d
--- /dev/null
+++ b/requirements-dev.in
@@ -0,0 +1,14 @@
+# Our direct dependencies used in development/CI.
+#
+# We generate requirements-dev.txt from this file by running
+#
+#     pip install -r requirements-dev.in && pip freeze > requirements-dev.txt
+#
+# and then modifying the file manually to restrict black and mypy to CPython
+
+pytest
+pytest-cov>=2.5.1
+mypy;implementation_name=="cpython"
+black;implementation_name=="cpython"
+check-manifest
+typing_extensions>=3.7.4;python_version<"3.9"
diff --git a/requirements-dev.txt b/requirements-dev.txt
index f6ac27d..7e6b598 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,5 +1,18 @@
-pytest
-pytest-cov>=2.5.1
-mypy;implementation_name=="cpython"
-black;implementation_name=="cpython"
-check-manifest
+black==23.3.0;implementation_name=="cpython"
+build==0.10.0
+check-manifest==0.49
+click==8.1.3
+coverage==7.2.7
+exceptiongroup==1.1.1
+iniconfig==2.0.0
+mypy==1.4.1;implementation_name=="cpython"
+mypy-extensions==1.0.0
+packaging==23.1
+pathspec==0.11.1
+platformdirs==3.8.0
+pluggy==1.2.0
+pyproject_hooks==1.0.0
+pytest==7.4.0
+pytest-cov==4.1.0
+tomli==2.0.1
+typing_extensions==4.7.0